U.S. Pat. No. 4,820,695 describes certain macrolide antibiotics. Using the description of U.S. Pat. No. 4,820,695, such a compound may be described as a compound of formula I: ##STR1## wherein R is a saturated or unsaturated secondary amino group of the formula ##STR2## in which the nitrogen atom is part of an otherwise carbocyclic ring system selected from a monocyclic ring containing from 5 to 16 ring atoms or a bicyclic or tricyclic ring system containing from 8 to 20 ring atoms or such a group wherein one or more of the carbon atoms is substituted by C.sub.1 -C.sub.4 alkyl, C.sub.2 -C.sub.4 alkenyl, C.sub.1 -C.sub.3 alkoxy, C.sub.1 -C.sub.4 alkoxycarbonyl, hydroxyl, C.sub.1 -C.sub.4 alkanoyloxy, halo, halo-C.sub.1 -C.sub.4 alkyl, --N(C.sub.1 -C.sub.4 alkyl).sub.2, --N(CH.sub.2).sub.m, ##STR3## cyano, ethylenedioxy, benzyl, phenyl, or phenyl substituted by from 1 to 3 substituent--substituents selected from nitro, halo, C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 alkoxy, hydroxy, amino, or mono- or di-(C.sub.1 -C.sub.4 alkyl) amino;
m is an integer from 4 through 7; PA1 R.sup.1 is ##STR4## R.sup.2 is hydrogen; C.sub.1 -C.sub.5 -alkanoyl or C.sub.1 -C.sub.5 -alkanoyl having from one to three halo substituents; benzoyl, phenylacetyl or phenylprionyl or benzoyl, phenylacetyl or phenylpropionyl having from one to five halo or methyl or from one to two methoxyl, nitro or hydroxyl substituents; PA1 R.sup.3 is hydroxy; C.sub.1 -C.sub.5 alkanoyloxy; C.sub.1 -C.sub.5 -alkanoyloxy having from one to three halo substituents; benzoyloxy, phenylacetoxy or phenoxyacetoxy or benzoyloxy, phenylacetoxy or phenoxyacetoxy having from one to five halo or methyl or from one to two methoxyl, nitro or hydroxyl substituents; or ##STR5## or an acid addition salt thereof.
A particularly useful formula I compound is one wherein R is ##STR6## R.sub.1 is an (a) group, R.sup.2 is H and R.sup.3 is hydroxy. It is known by the non-proprietary name tilmicosin, assigned by USAN, the United States Adopted Names organization. It has the following structural formula: ##STR7##